The present invention relates to a graphic recording device that incorporates a variable speed thermo-responsive sheet material wherein any character including selected alpha-numeric or scientific characters are imprinted on the sheet material thermographically. The characters may be either read and interpreted directly or by further machine processing. In variations of the device, with appropriate changes, other type responsive sheets, i.e., an electro-sensitive or electro-graphic sheet may be utilized in place of the thermo-sensitive recording sheet. Generally, sensitized chart paper in roll form is utilized, however, other sheet form materials such as cloth, plastic, etc. can also be used.
This present invention has particular application in analog recorders incorporating variable speed chart records made on thermo-sensitive sheet material, which may be used to monitor continuously changing physiological information such as electrocardiography (ECG), electroencephalography (EEG), blood pressure, inter-ocular pressure, or scientific data such as ph, voltage, current, etc.
In such cases it is not only necessary to identify the patient from whom such data is being taken where many patients are being monitored, but, increasingly, sophisticated diagnoses of the continuously varying data are being made by computer and fed back to the analog recorder. In such instances, the analog channel, or channels, of the recorder display the continuously changing data, such as ECG, in the classical wave form manner for conventional analysis by those skilled in the art, while one or more printer channels utilizing the instant invention can receive simultaneous computer analysis in alpha-numeric form which would be printed out on the same thermo-responsive sheet, adjacent to the analog data, much like a conventional tele-typewriter, thereby enhacing a diagnosis of patient condition.
Because different physiological data, and other scientific data are recorded at different chart speeds, it is important that the fixed print head be capable of imprinting alpha-numeric and other characters on the sheet as the sheet moves in operative contact therewith at such varying sheet speeds, without blurring the characters or without elaborate prior adjustment to prevent such blurring. In previous devices, characters were imprinted on analog recorder charts by mechanical print heads which used carbon paper or typewriter style ribbons, or inking pads. Others utilized thermo-responsive papers in combination with segmented printer heads. In the case of segmented print heads the characters are formed when horizontal and vertical elements or bars, usually seven in number, are arranged in a matrix or mosaic pattern so that by selectively energizing, i.e. heating, one or more of the bars in such matrix, an identifying mark will occur at that location on the thermo-responsive sheet where such bar physically or operatively contacts the sheet. The mark will accordingly be an exact size and shape reproduction of the mosaic or matrix pattern of the energized bar or bars. An example of such a segmented mosaic or matrix type print head is disclosed in U.S. Pat. No. 3,754,279 dated Aug. 21, 1973.
As can be readily seen, the number and variety of characters that can be formed by such known segmented bar systems is limited. For example the letter "X", the asterisk, the symbols for parentheses, commas, slant lines, accent marks, question marks or scientific symbols, or reproductions of analog data either cannot be formed at all or cannot be readily formed. Also, upper and lower case designations of the same letters cannot be conveniently formed with a single matrix pattern print head. Attempts have been accordingly made to improve both the range of characters printable by such matrix type segmented print heads as, for example, by superimposing layers of segment print heads over each other wherein the bars from one layer overlap other layers thereby avoiding the gaps which are characteristic of segment print heads. Despite these improvements, an unlimited range of characters and reproductions of analog data cannot be formed even with such improved matrix type print heads. A need thus exists for a print head so constructed as to enable expanded and more versatile printing within the above indicated environment.
Additionally, recording devices of the above discussed type require an advancing means most generally in the form of friction-related drive rolls to advance a supply of sheet material, normally in roll form, from a storage position through the device. Such advancing means may thus serve to move the sheet past a recording stylus in turn movable transversely across the sheet in response to varying electrical impulses from an interconnected galvanometer, and past a printing head which effects the printing of indicia identifying the above indicated information transferred to the sheet. A convenient mechanism for thus storing such sheet material in roll form within the device but making such readily available for replenishment would be desirable.
Furthermore, devices of this nature normally include a bar or knife edge transversely disposed to the longitudinal path of sheet travel so that when information from a particular patient or the like has been concluded, the relevant portion of the sheet may be torn from the supply for analysis or for reference filing with a patient's records. Also, inasmuch as devices of this nature may require that the sheet assume a plurality of transverse bends of a rather complicated nature so as to insure passage past the essential functional portions of the device in the proper attitude within an essentially limited space, it would be desirable to provide a mechanism for supporting and disposing such sheet material initially from a storage or nonoperative position through intermediate positions and into an active or operative position automatically and without the necessity of requiring the operator or observer of the device to consume the time that would be necessary to hand thread such sheet material.
Accordingly, a primary object of the present invention is the provision of a printing head of straightforward simple construction for use in an information recording device of the aforementioned type and wherein an unlimited number of characters including those incapable of being formed by segmented matrix type print heads, are formable.
A further object of the invention is the provision of a print head which includes a series of spaced segments or elements aligned in transverse disposition to the path of sheet travel so that activation of one or selected numbers of such segments can be utilized to alternately form either discrete separated marks or continuing lines on such sheet surface dependent on the activation dwell time of such segment or segments.
A still further object of the present invention is the provision of a printing head for use in information recording devices of the aforementioned type in which a plurality of separate, spaced segments or elements thereof are disposed with regard to the sheet material so that the regulation of the speed of travel of such sheet material past such print head may be utilized to regulate one of the major dimensions of the characters formed thereby.
A further object of the invention is the provision of a method of the immediately aforementioned type wherein the sequential activation of a plurality of spaced mark-forming segments disposed transversely of the path of sheet travel serves to regulate one major dimension of the characters so formed and the speed of travel of such sheet in combination with the activation interval of such segments provides the remaining major dimension to such characters.
A still further object of the invention is the provision of a device of the aforementioned type which will provide individual marks on a traveling sheet of material which will not be blurred.
Another primary object of the present invention is the provision of a novel and convenient mechanism for automatically positioning a running length of sheet material in simultaneous operative contact with the information recording means of a device of the aforementioned type.
A still further object of the invention is the provision of a sheet handling mechanism which incorporates a supply of such material in a member adapted for pivotal movement in relationship to the remaining portions of the device so that a running length of such sheet material may be automatically supported and guided through a tortuous path and automatically placed in operative association with the advancing means, the recording means, and the printing means of a device of the aforementioned type.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.